I want to have different mounts that are seen only by a specific process or user. One use case I am thinking about is when I want to mount a unionfs or aufs that will be available for one user. So I can have multiple mounts on the same mount point that are different for different users.
Why not just mount at ~/specificmountpoint. Set the permissions accordingly. Every user will have the same (almost) mout point.
It looks like nowadays it's possible:
At least, in theory. Check this article for more details: http://lwn.net/Articles/531114/
Here is how to enable per user mount namespaces in Ubuntu 12.10 using pam_namespace:
Uncomment the last lines. For safety, add your current user to the list of exclusions.
For testing edit
Test on a test user:
As test user run:
This will generate a command like:
Run the generated diff from test user shell and from root. From the test user you will have no output, but from the root you will see something like: